Rotary valves may be used to regulate the flow of liquid or gas through a system. In one example, one or more rotary valves may be included in a thermal management module (TMM) to regulate coolant in a vehicle's power or drive train. For example, after the engine is started, the TMM may block off the cooling jacket so that the engine heats up faster. When the engine has reached its optimum operating temperature, the TMM may open a coolant circuit and use the available heat to regulate the temperature of the engine, transmission, heating system, and/or other system components. The rotary valve(s) in the TMM may control the flow of coolant to the various components in the system.